A Novel and Green Method for the Synthesis of Highly Substituted Isoquinoline Derivatives in Ionic Liquid

A series of new highly substituted isoquinoline derivatives was obtained from the reaction of 2-(1-substituted piperidin-4-ylidene)malononitrile, benzaldehyde and malononitrile or cyanoacetate in ionic liquid at 50 degrees C. This novel procedure was different from the previous method in the synthesis of isoquinoline using pyridine fragment as reactant to construct benzene ring, and as well as had the advantages of one-pot, mild and environmentally benign. A possible mechanism was proposed based on the further experimental results.